Recording data on motion picture film

ABSTRACT

A film record comprises a film strip representing a plurality of frames. At least one of the frames includes at least one region wherein the optical density of the region is representative of a symbol from a constellation of symbols.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit under 35 U.S.C. §120 and is a divisionof U.S. patent application Ser. No. 10/559,110 filed Dec. 2, 2005 nowU.S. Pat. No. 7,508,484, which is a 35 U.S.C. §371 national stageapplication of PCT/US04/019005 filed Jun. 16, 2004, and published inaccordance with PCT Article 21 (2) on Dec. 29, 2004 in English and whichclaims the benefit of U.S. provisional patent application No.60/479,433, filed Jun. 18, 2003.

BACKGROUND OF THE INVENTION

The present invention generally relates to apparatus and methods forrecording data on film.

Many applications require the storage of very large quantities of datafor long periods of time. One example is found in the production ofmotion pictures or movies. Traditionally, a movie was made by shootingan original camera negative (OCN), which was then edited by cutting andsplicing operations. More recently, the use of digital special effectshas introduced a requirement for some parts of the OCN to be “scanned”to convert each frame of film into a set of digital data, whichrepresents the frame film image information. Similarly, when an oldmovie is to be restored using digital techniques it may be necessary toscan all of the film so as to obtain a digitized version of the entiremovie (a digital film record).

The process of scanning a film to create a digital film record isexpensive and time consuming, and each use of the OCN increases thepossibility of damage. Hence, it would be advantageous to treat thedigital film record itself as the archive of the content, rather thanthe traditional approach of creating three monochrome separations onfilm and archiving those.

In this regard, the scanning process generates very large quantities ofdata. Today, most film scanning is performed at a resolution of “2K”,meaning 2048 pixels horizontally by 1536 pixels vertically (or similarresolutions generating similar quantities of data). Generally each pixelis represented by a digital value for each of red, green, and bluerepresentative signals, where each digital value has a precision of atleast ten bits. This means that more than 11 MB (millions of bytes) ofdata is generated for each frame of a film. There are normally 24 framesin a second of film, yielding an effective data rate of approximately300 MBps (megabytes per second). Thus, a 2-hour movie would berepresented by more than 2 terabytes (TB) of data, where, for purposesof this description, each terabyte is defined herein as being equal to1,000,000 MB.

However, data storage requirements will continue to increase. Forexample, scanning a film with a “4 k” resolution, and 14-bit precision,generates about 66 MB for each frame of film. In addition, if digitaltechniques are used for all of the production it may be necessary toscan an OCN that exceeds by many times the duration of the final movie.These additional factors mean that the data storage requirements for asingle movie may reach many tens of terabytes.

Such quantities of data are very difficult to handle and store. Currentdata tape mechanisms can transfer data to tape at a rate ofapproximately 50 MBps, and provide storage of approximately one half ofa terabyte on a single tape. Using such a device, transferring a 2-hourmovie at a 2K resolution to tape would require four tapes and takenearly twelve hours to complete.

Another problem with storage of data is longevity. Most magnetic mediasuch as tape, and optical storage media such as CDs and DVDs, haveexpected lives of a few tens of years. These life spans are quiteunacceptable for archival purposes. In comparison, the science ofarchiving film is well developed, and color film can be maintained ingood condition for many tens of years, while monochrome separations onmodern stock are expected to have a useful life of hundreds of years.

Film records are, in fact, quite different from most forms of records.For example, in magnetic recording or optical recording it may bepossible to overwrite or destroy the record. In particular, in magneticrecording, elements are magnetized in a certain direction during therecording process. Clearly the same elements can be de-magnetized orre-magnetized by a re-application of the recording process. Similarly,while optical records generally take the form of physical indentationsin a surface, or alterations in a dye layer which result in a localizedchange in the optical properties of the layer, that are not easilyaltered, it may be possible to overwrite, or at least to destroy, theoptical record by a reapplication of the recording process.

In contrast, in a film record the application of light to photographicfilm (exposure) causes a latent image that is then subjected to achemical “development” process so that the image is substantiallyreinforced. Unexposed emulsion is then removed by a process known as“fixing”. The combination of these processes yields a very robust recordthat can no longer be overwritten by re-exposure, or damaged by anythingbut extreme physical processes.

Although the movie industry has been used as an example, many otherbusinesses create large amounts of data and have needs for archivalstorage of this data. It is interesting to note that the longevity offilm records compared to other available storage mechanisms has beenrecognized in the data industry. Some companies such as Anacomp, Inc.offer services to businesses requiring long-term storage of computerdata records. In one mechanism, data records are imaged as characterdisplays on (for example) a cathode ray tube and recorded on film,usually 16 mm (milli-meter) or 105 mm microfiche. An example of thistechnology is described in U.S. Pat. No. 4,553,833, issued Nov. 19,1985. In this patent, light emitted from a relatively large-sized array(such as a light emitting diode array) is focused through converginglenses to cause a relatively small-sized dot pattern to be projected ona film. While this approach yields records that can provide the desireddegree of permanence, the data density is relatively low (perhaps 100 to1000 bytes/mm²) and hence the technique is not suited to storage of verylarge data records.

It should be noted that binary data may also be recorded directly ontofilm as a pattern of black and white dots representing values of onesand zeroes. Generally some sophisticated coding scheme is used toimprove the effective data density and to provide error correctioncapability to ensure robustness. These techniques have been usedextensively for recording audio data onto the edge of a motion picturefilm. For example, U.S. Pat. No. 4,600,280, issued Jul. 15, 1986,describes a technique for recording a digital soundtrack on a film stripby exposing the film to modulated light from a light source. In onemethod disclosed therein an intermittent light beam (encoded withdigital audio information) is scanned horizontally across the film, andthe film is then advanced vertically and the scanning process repeated.This patent also describes that the light can be projected on the filmthrough a linear array of solid state shutters or Bragg cell modulators.

Other examples of storing data on film are described in the followingU.S. patents. U.S. Pat. No. 4,461,552, issued Jul. 24, 1984, describes amethod for photographically recording digital audio on motion picturefilm. U.S. Pat. No. 4,306,781, issued Dec. 22, 1981, describes recordinga command data track on motion picture film, along with an unmodulatedlocator and several analog soundtracks. Similarly, both U.S. Pat. No.4,659,198, issued Apr. 21, 1987, and U.S. Pat. No. 4,893,921, issuedJan. 16, 1990, describe a process for recording digital data along anedge portion of a strip of cinematographic film. And, U.S. Pat. No.5,453,802, issued Sep. 26, 1995, discloses a method and apparatus forphotographically recording digital audio signals, and a medium havingdigital audio signals photographically recorded thereon.

In general, the technology represented by the above-described patentsprovide a very robust signal that can survive the two printing processesgenerally necessary to generate a movie release print, and that isreasonably tolerant of minor damage that can occur with use,particularly to edges of a release print. Unfortunately, the recordingdensity is below one kilobyte/mm², which is too low for use in providinglong-term archival storage of large amounts of data such as representedby, e.g., a digital film record.

SUMMARY OF THE INVENTION

In accordance with the principles of the invention, a medium having datastored thereon comprises a film, wherein portions of the film representdifferent optical density values; and wherein each level of opticaldensity is associated with a symbol from a constellation of symbols. Asa result, the inventive concept provides for a method and apparatus forrecording data that not only takes advantage of the exceptionallongevity of a film record—but also provides recording density valuessignificantly higher than one kilobyte/mm².

In an embodiment in accordance with the principles of the invention, afilm record comprises a film strip representing a plurality of frames.At least one of the frames includes at least one region wherein theoptical density of the region is representative of a symbol from aconstellation of symbols.

In another embodiment in accordance with the principles of theinvention, a recording system comprises an encoder and a mapper. Theencoder receives data to-be-recorded and provides encoded data to themapper. The latter selects optical symbols, from a constellation ofoptical symbols, as a function of the encoded data. The film is thenexposed to represent thereon the selected optical symbols to provide a“density film record.”

In another embodiment in accordance with the principles of theinvention, a system comprises a reader, which includes a decoder. Thereader processes a density film record to recover therefrom encodeddata, which is provided to the decoder for recovery of the data.

In another embodiment in accordance with the principles of theinvention, a data cartridge transports a film strip, wherein portions ofthe film strip represent different density values; and wherein eachlevel of density is associated with a symbol selected from aconstellation of symbols. The data cartridge further comprises anidentifier that represents content-related information (meta-data)pertaining to the data stored on the film strip. Although not limited tothe following examples, this meta-data may comprise one, or more, of thefollowing items: title, dates, source history, processing history priorto recording, etc. In accordance with a feature of the invention, theidentifier represents one or more of the following: a label of readabletext, a bar code, a magnetic strip, radio frequency identification(RFID) tag and/or a solid state memory chip (e.g., that is capable ofbeing programmed with identifying information).

In one illustrative variation of the above-described embodiments, thedata stored on the film record represents a digital film record.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a prior art 16QAM symbol constellation;

FIG. 2 illustrates the inventive concept;

FIG. 3 shows an illustrative embodiment in accordance with theprinciples of the invention;

FIG. 4 shows another illustrative embodiment in accordance with theprinciples of the invention;

FIGS. 5-11 illustrate recording data on film in accordance with theprinciples of the invention;

FIG. 12 shows another illustrative embodiment in accordance with theprinciples of the invention;

FIG. 13 shows an illustrative flow chart in accordance with theprinciples of the invention;

FIG. 14 shows another illustrative embodiment in accordance with theprinciples of the invention;

FIG. 15 shows another illustration of recording data on film inaccordance with the principles of the invention;

FIGS. 16-19 show other illustrative embodiments in accordance with theprinciples of the invention;

FIG. 20 shows another illustrative flow chart in accordance with theprinciples of the invention; and

FIGS. 21-23 show other illustrative embodiments in accordance with theprinciples of the invention.

DETAILED DESCRIPTION

As described further below, the inventive concept provides the abilityto store large amounts of data for long periods of time using a provenarchival medium—film. One application of the inventive concept is in theentertainment industry. In particular, the inventive concept provides asafe, reliable and cost effective archival solution for storing digitalrich media content such as a digital film record.

Other than the inventive concept, the elements shown in the figures arewell known and will not be described in detail. For example, other thanthe inventive concept, film processing, modulation transfer function,error detection and correction, encoding and decoding, modulation anddemodulation, symbol mapping, etc., are well known and not described indetail herein. In addition, the inventive concept may be implementedusing conventional programming techniques, which, as such, will not bedescribed herein. Also, as used herein, the term “monochrome film”refers to a film having only a single emulsion layer and not capable ofrecording information that distinguishes between colors, i.e.,monochrome film is “black and white” film. Such films include typesknown as orthochromatic and panchromatic. The term “monochrome” does notimply any particular spectral sensitivity. In addition, as used herein,the term “optical density” (OD) is defined as known in the art. Forexample, for a given wavelength, optical density is an expression of thetransmittance of an optical element. Optical density can bemathematically expressed as log₁₀(1/T), where T is transmittance, i.e.,the higher the optical density, the lower the transmittance. Finally,like numbers on the figures represent similar elements.

As described earlier, previous techniques of recording data on filmoperate in a binary manner—any particular area of film is either exposed(black and opaque in the negative film image) or not exposed (clear andtransparent in the negative film image). While transition zones (areasof partial transparency) between exposed and nonexposed areas may existin these previous techniques, these transition zones are not used forstoring data.

In contrast, the inventive concept takes advantage of the fact that filmis capable of reproducing a wide range of gray levels (differing degreesof transparency) with good accuracy to increase the quantity of datathat may be stored on a given area of film. In particular, the inventiveconcept applies the idea of “symbols” from digital transmission systemsto storing data on film.

Digital transmission systems, used in modems and other communicationsystems, code multiple bits by using differing levels of a carrier, orof multiple carriers. The various levels, or combinations of levels,form a “constellation” of permissible values or symbols. Mostfrequently, a symbol constellation is used that has a number of symbolsthat is a power of two, and each symbol represents a number of bits thatcorresponds to the particular power of two. For example, if there areonly two symbols in a constellation, i.e., (2¹) symbols, only one bit ofinformation is represented (one symbol represents a value of “0” and theother symbol represents a value of “1”). Likewise, for a constellationcomprising four symbols, i.e., (2²) symbols, as used in the well-knowntransmission coding systems 4VSB (4-level Vestigial Sideband), QPSK(quadrature phase-shift keying) and 4QAM (4-level quadrature amplitudemodulation), each symbol represents two bits of information, where thetwo bits have the possible values: 00, 01, 10 and 11. Similarly, otherwell-known coding schemes permit even more bits to be encoded, such as8VSB (each symbol represents 3 bits), 32QAM (each symbol represents 5bits), and 256QAM (each symbol represents 8 bits), etc. As furtherillustration, a prior art 16QAM symbol constellation 25 is shown inFIG. 1. Symbol constellation 25 comprises 16 symbols (2⁴), each symbolrepresenting a particular four bit value. For example, symbol 26represents the four bit value “0101.”

Therefore, and in accordance with the principles of the invention, arange of optical density levels (differing degrees of transparency) thatcan be reproduced in a film are representative of various symbols of aconstellation, where each symbol represents a plurality of bits. This isillustrated in FIG. 2. The latter shows a simple application of theinventive concept in the context of mapping four bits of data to one ofsixteen optical density levels, or optical symbols. As shown in FIG. 2,each four bit data value is mapped to a particular optical densitylevel. For example, the four bit value “0101” is mapped to OD level 6 asillustrated by dashed arrow 41. Illustratively, each OD level isassociated with one of 16 gray levels. For example, OD level 6 isassociated with gray level 57 as illustrated by dashed arrow 51 and ODlevel 2 is associated with gray level 58 as illustrated by dashed arrow52. As used herein, the term “optical symbol” refers to a particularoptical density level, e.g., a particular gray level as shown in FIG. 2.

Turning now to FIG. 3, a further illustration of the inventive conceptis shown for storing data on film. An input data signal 104, whichconveys data, is applied to recording system (recorder) 100 for storageof the data on film 150. The latter is illustratively monochrome film.Although not required for the inventive concept, with respect to anarchiving application monochrome film has the greatest stability andlongevity. Recorder 100 includes a mapper 115 and light source 120. Theinput data signal 104 is applied to mapper 115. Input data signal 104 isrepresentative of one, or more, input data signals (e.g., data presentedin serial or parallel form). For example, in the context of FIG. 2,input data signal 104 conveys four bits of data every symbol interval,T. Alternatively, input data signal 104 may represent one, or more, bitsof data that are accumulated over time by mapper 115 to form the fourdata bits every T symbol interval. Mapper 115 maps the input data signalto one of a number of optical symbols every symbol interval T. Eachresulting symbol is provided via signal 116 to light source 120. Again,in the context of FIG. 2, there are sixteen optical symbols, eachoptical symbol associated with a corresponding gray level.Illustratively, light source 120 exposes areas of film 150 (as usedherein, areas of film are also referred to as picture elements orpixels) to varying degrees, via exposure signal 121, to record one of aplurality of optical symbols (levels of partial transparency) at eachpixel location, so that a plurality of bits of information may berepresented by the optical symbol or transparency of each pixel. Film150 advances a frame at a time in the direction illustrated by dashedarrow 2. A blank frame is illustrated by frame 150-1 of film 150, arecorded frame is illustrated by frame 150-2 of film 150. Light source120 is representative of any known mechanisms that can record an imageto film. For example, light source 120 is a laser recorder that isdesigned to write high quality conventional analog images to film. Thisis a known color device with three lasers intended to expose the threelayers of a color film, but in the context of FIG. 3 a single laser needonly be used with monochrome film 150. Other devices, including, but notlimited to, LCDs (liquid crystal displays) and cathode ray displays, mayalso be used to record film images. Each would have differentcharacteristics that affect the achievable density, i.e., the number ofsymbols that may be recorded along the length and width of the film.Important parameters that differ among such devices are addressability,speed, resolution, optical blooming, etc. Following the recordingoperation the exposed film is processed (developed and fixed) so as toreveal the latent image, and to make the record permanent. This isillustrated in FIG. 4, where film 150 is further processed by element170, which includes chemical processing and drying as known in the artfor making the record permanent. Element 8 shown in FIG. 4 isrepresentative of one of a number of capstan drives that utilizemechanized spindles to move film 150 through the apparatus. It should benoted that the details of processing can also be variable, and canresult in different contrast laws and other characteristics of theimaging system.

Although illustrated in the context of 16 optical symbols, it should benoted that a relatively large area of film can accurately convey a largenumber of optical symbols. For example, 1024 varying degrees of graylevels can be used, i.e., a symbol constellation of 2¹⁰ optical symbols,each optical symbol representing 10 bits of data. On the other hand, avery small area of film can accurately distinguish a lesser number oflevels. In part this is due to limitations that must exist in thepositional accuracy of the recording and reading processes. Also, a verysmall area will be subject to a degree of uncertainty because of therandom nature of film grain, and of the manner in which film grain is“clumped”. These effects are the equivalent of noise on the recoveredsignal, and reduce the ability to distinguish between recorded graylevels.

In accordance with the principles of the invention, an illustrativeportion 151 of a film is shown in FIG. 5 after exposure. As can beobserved from FIG. 5, portion 151 comprises a number of optical symbolsrecorded along both the X (length) and Y (width) dimensions of the film.Illustratively, the optical symbols are represented by various graylevels, each optical symbol representing a plurality of data bits. Afurther film portion 152 is identified in FIG. 5 and is shown in moredetail in FIG. 6. As can be observed from FIG. 6, film portion 152 isrepresentative of recording data using a symbol constellation of 2⁸optical symbols, e.g., 256 gray levels ranging from gray level #1 togray level #256. In particular, arrow 67 illustrates the use of graylevel #38, which is predefined as representing the eight bit value“00100110.” A further film portion 153 is identified in FIG. 6 and isshown in more detail in FIG. 7 to further illustrate the inventiveconcept.

Turning now to FIG. 8, film portion 153 is again reproduced toadditionally illustrate the inventive concept. Illustratively, eachframe of a film is divided into a number of pixel regions, each pixelregion conveying therein an optical symbol. These pixel regions can bearranged in any fashion. As used herein, the term “pixel region” used toconvey a symbol is also referred to as a “write spot” or a “data dot.”One arrangement is shown in FIG. 8 and is a simple rectangular array ofpixel regions having rows, as illustrated by arrow 88, and columns, asillustrated by arrow 89. A column of pixel regions, 95, is furtherillustrated in FIG. 9. Each column extends between film boundaries 93and 94. The latter represent the boundaries of the usable portions ofthe film, i.e., the available width of the film (the available width ona 35 mm print is 23 mm). Although not necessary to the inventiveconcept, guard regions may also exist between pixel regions, betweenrows and/or between columns, or any combination thereof. Guard regionsmay be used for synchronization purposes and/or spatial adjustment foraccurately locating regions on the film. For example, guard regions maybe arranged around each pixel region resulting in a checker-board likepattern of used and non-used pixels. Guard regions may also includeidentifiable synchronization (sync) patterns to permit electronic ormechanical adjustment of the recording mechanism and reading mechanism(described below). It should be noted that guard regions reduce theamount of film used to store data and, therefore, affect the amount ofavailable storage space. Illustratively, FIG. 9 shows the use of guardregions 91 and 92 (also referred to as gaps 91 and 92) between arespective film boundary and a column of data dots. Each columncomprises a number of data dots or pixel regions. The column shown inFIG. 9 illustrates twelve pixel regions, each region conveying an 8 bitsymbol as shown in FIGS. 6 and 7. Although not required for theinventive concept, each pixel regions is illustratively rectangular inshape having a height, H, and a width, W, as shown in FIG. 9 for pixelregion 96. An illustrative arrangement of such a frame is shown in FIG.10. Frame 160 comprises a rectangular array of optical symbolsrepresented by symbols 161 and 162 comprising J columns and I rows,wherein each optical symbol represents a plurality of bits. It should benoted that the gray levels shown in symbols 161 and 162 are forillustration only in order to contrast the elements of the array. Asnoted above, other arrangements are possible, e.g., a checker-boardpattern, where guard regions are disposed around each symbol areillustrated in frame 165 of FIG. 11. It should be noted that frames 160and 165 shown in FIGS. 10 and 11 represent the usable area of the frame.

In terms of recording, the following should be noted. Currently, amaximum achievable resolving power is below 4000 resolvable elements ina frame. A 2K digitized image resolution is a theoretical maximum, sinceit needs more than 4000 resolvable elements (Nyquist Theorem), or 2000line pairs in a frame. Thus, the MTF (modulation transfer function)resolving power requirement on a recorder is 2000/23 or 87 linepairs/mm. It should also be noted that 60 pairs per mm is the optimumtoday for a color film printing process. In addition, film grain alsorepresents a constraint on recording density or line pairs per mm.Effects may be mitigated by shaping the signal before recording (e.g.,predistortion), and performing complementary processing of the recoveredsignal. Grain noise is partially predictable and can be withdrawn by asuitable algorithm. In view of the above, black & white fine grain printstock can provide resolution beyond that of the color film printingprocess (for example, in excess of 100 line pairs per mm).

As noted above, pixel regions (write spots) can be of any shape and theshape of a write spot can be further optimized to improve recordingdensity and therefore media utilization. Furthermore, the area betweenconventional film frames can be utilized to increase the total capacityof the film. If necessary, synchronization (sync) words can be insertedinto the data to facilitate its subsequent reconstruction. Thus thereappears no requirement to repetitively shutter the film exposure toconstrain write spot placement within the boundaries of a projectionfilm image.

Also, unlike telecine scanning of film where the complete 35 mm imagearea contains information, subsequent recovery of data requires that thedata dots be scanned or sampled rather than any gaps between. To thisend, it may be preferable that the data is formatted such that acontinuous clock signal can be recovered independently of the datavalue. For example, data dots are written across the film frame area ina continuous manner without use of a film gate or shutter as the mediumis transported in a smooth continuous manner. Each horizontal write scanwill include header data to provide spatial identification of the imagestrip and to initiate clock recovery to enable reader track following.

It should be noted that recording optimization parameters may need to beadjusted to compensate for flare in a recorder. Recorder flare may occurdue to on/off cycle time on adjacent spots (high contrast from white todark adjacent spots, in addition to beam spread, causes blooming). Suchimpairments are in general directly related to the intensity of theilluminating spot hence an algorithm can be employed, if necessary, toorganize data dot placement in accordance with spot intensity (datavalue) and the value of spatially adjacent spots. For example adjacentbright spots can be differentiated more accurately than adjacent spotsof significantly different intensity. In this way the dot pitch will bedot brightness modulated or responsive to the data value. Alternatively,dots can be recorded in differing film layers in accordance with theirdata values, i.e., physically separate dim, medium and bright data dotvalues to reduce or eliminate inter-symbol interference. Likewise, theremay be intrinsic stock flaws in film, e.g., “coating holidays” aredensity variance defects causing spot irregularities that may requireuse of, e.g., forward error correction (FEC) to correct recovery errors.

Reference should now be made to FIG. 12, which illustrates anotherembodiment of a recorder in accordance with the principles of theinvention. Recorder 200 of FIG. 12 is similar to recorder 100 of FIG. 3except that recorder 200 now includes forward error correction (FEC) asrepresented by FEC encoder 105. Any form of FEC encoding may be used,e.g., Reed Solomon coding, trellis coding, etc. The purpose of FECencoding is to compensate for possible transmission channel impairments(here the transmission channel is represented by film 150). As can beobserved from FIG. 12, FEC encoder 105 operates on input data signal 104to provide an encoded data signal 106 to mapper 115, which maps theencoded data signal to optical symbols selected from an optical symbolconstellation, as described above. Thus, a high data rate and low errorrate may be achieved by a suitable choice of coding scheme.

In view of the above, an illustrative flow chart in accordance with theprinciples of the invention for recording data on film is shown in FIG.13. Reference should also be made to FIG. 14. In step 305, a recorder(e.g., recorder 100 of FIG. 3 or recorder 200 of FIG. 12) receives datafor storage on a film (blank frame 150-1 of FIG. 14). In step 310, therecorder maps the received data to one of a number of optical symbolsselected from a constellation of optical symbols. It should be notedthat in the context of FIG. 12, step 310 includes the step of encodingthe received data in accordance with an FEC code. In step 315, therecorder records the selected optical symbols on the film (illustrativerecorded frame 150-2 of FIG. 14) to create a density film record.

Since the inventive concept provides for the ability to store largeamounts of data on film, the information represented by the data caninclude one, or more, different types. For example, content information(meta-data) pertaining to a digitized movie stored therein can berecorded on the film. Although not limited to the following examples,this meta-data might include items such as title, dates, source history,processing history prior to recording, etc. This meta-data can be storedanywhere in a film. One illustration of a film format is shown in FIG.15, wherein the meta-data is stored as a header 154 on recorded film150. The header comprises one or more frames of film 150 occurring at orsubstantially near the beginning of the film. Illustratively, theheader, or leader, portion describes the encoding method in, e.g.,English. In other words, the header information is recorded as an imagesuch that it is readable by a person. This header information mayinclude actual source code (e.g., in the “C” programming language) thatis used to extract the data. Alternatively, each frame of film 150 canhave predefined regions that, e.g., comprise content related information(such as meta-data), data (e.g., video), etc. In this regard, attentionshould now be directed to FIG. 16, which illustrates that a variety ofdifferent types of information may be stored on film 150. For example, anumber of signals, N, representing different types of information areapplied to combiner 195. The latter, e.g., time-division multiplexes theapplied signals to form the above-described input data signal 104, whichis applied to recorder 200 for storing the various types of informationon film 150. For example, in the context of N=3, signal 103-1 representsthe above-noted meta-data, signal 130-2 represents video information andsignal 103-3 represents audio information. Other examples of types ofinformation that can also be recorded on the film are information aboutcoding scheme(s), instructions on recovery technique(s), etc. It shouldbe noted that combiner 195 merely illustrates the ability to storedifferent types of information on a film. As such, this function mayalso be performed within a recorder and may not require an actualcombiner element.

As described above, the inventive concept provides the ability to storelarge amounts of data using a proven archival medium—film. As such, forthose applications involving long-term storage, it is preferable thatthe film, e.g., film 150 described above, be conveyed in a hermeticallysealed “data cartridge” that can withstand the effects of long-termstorage. Such a data cartridge 190 is illustrated in FIG. 17. Thehousing 192 of data cartridge 190 includes film 150, e.g., amonochromatic polyester-based film stock. Other than the inventiveconcept, data cartridge 190 is constructed as known in the art, e.g.,data cartridge 190 is ruggedized and hermetically sealed to preservefilm 150, reduce human handling and assist in minimizing decay overtime. Data cartridge 190 can either be used to transport blank film suchthat the data cartridge itself is inserted into a recorder (e.g.,recorder 100 or recorder 200, described above) for recording of data, ordata cartridge 190 can be used to subsequently store recorded filmtherein. Data cartridge 190 may additionally contain content information(meta-data) pertaining to the data stored therein as represented byidentifier 191. Although not limited to the following examples, thismeta-data might include items such as title, dates, source history,processing history prior to recording, etc. Identifier 191 representsone or more of the following: a label of readable text, a bar code, amagnetic strip, a radio frequency identification (RFID) tag and/or asolid state memory chip (e.g., a memory chip that is capable of beingprogrammed with identifying information). It should be noted that theabove-described recording process may be further modified toautomatically provide information to identifier 191. For example, in thecontext of readable text, identifier 191 may be printed by the recordingdevice. Likewise in the context of a bar code. Or, in the context of amagnetic strip or solid state memory, identifier 191 may beautomatically programmed with the meta-data. The use of machine-readablemetadata would advantageously provide for the ability to utilizeautomated & mechanical handling, e.g., robotic shelving of a datacartridge.

Additional variations, and combinations of variations, to theabove-described data cartridge 190 are possible. For example, in onevariation data cartridge 190 is reusable in the context that the filmstored within is replaceable. Similarly, in another variation, datacartridge 190 contains all the chemicals necessary for processing thefilm (e.g., reference to element 170 of FIG. 4). In other words, thefilm and chemicals are a part of a single assembly—thus, reducing thenumber of parts necessary to operate the system. In this context, usedchemicals are preferably returned to a container (not shown) whenprocessing is complete for recycling.

Referring now to FIG. 18, an illustrative apparatus 400 is shown inaccordance with the principles of the invention for reading a film.Other than the inventive concept, reader 400 may be a conventional filmscanner. Reader 400 comprises light source 425, detector 420 anddemapper 415. This apparatus performs the complimentary functionperformed by recorder 100 of FIG. 3. A recorded film 150 (as representedby frame 150-2) moves through reader 400 a frame at a time. Each frameis illuminated by light source 425 via illumination signal 426. Theresulting projected image 427 is applied to detector 420, which measuresor assesses the corresponding OD level on at least one of the pixelregions of frame 150-2 and provides the corresponding value to demapper415, via signal 421. Demapper 415 provides the associated bit value viasignal 406. For example, in the context of the bit-to-symbol mappingshown in FIG. 2, a detected gray level 57 is converted by demapper 415into a four bit value of “0101”. As noted above, meta-data informationmay be recorded on film 150. Although not required, it is preferablythat this meta-data is stored in a header of film 150 as illustrated inFIG. 15 so that the meta-data can be initially accessed upon reading ofthe film.

It should be noted that an element impacting the efficiency of a readeris the accuracy of reading the gray levels. Given that there may bevariations in the exposure and processing mechanisms, the reading methodpreferably employs reading of areas that represent maximum and minimumrecorded densities so as to calibrate the reading and determination ofthe intermediate gray levels. Extensions to this process may includemeasuring known intermediate values so that the reading device cancalculate the transfer characteristic of the system and more accuratelydistinguish adjacent gray levels at all parts of the transfercharacteristic.

Turning now to FIG. 19, another illustrative apparatus 500 is shown inaccordance with the principles of the invention for reading a film.Reader 500 is similar to reader 400 except for the addition of FECdecoder 405. As such, reader 500 performs the complimentary functionperformed by recorder 200 of FIG. 12. A recorded film 150 (asrepresented by frame 150-2) moves through reader 500 a frame at a time.Each frame is illuminated by light source 425 via illumination signal426. The resulting projected image 427 is applied to detector 420, whichmeasures or assesses the corresponding OD level on at least one of thepixel regions of frame 150-2 and provides the corresponding value todemapper 415, via signal 421. Demapper 415 provides the associated bitvalue via signal 416. For example, in the context of the bit-to-symbolmapping shown in FIG. 2, a detected gray level 57 is converted bydemapper 415 into a four bit value of “0101”. This bit value representsencoded data and is applied to FEC decoder 405, which recovers the dataencoded therein and provides the recovered data via signal 406.

In view of the above, an illustrative flow chart in accordance with theprinciples of the invention for reading data on film is shown in FIG.20. In step 350, a reader (e.g., reader 400 of FIG. 18 or reader 500 ofFIG. 19) receives a film and scans each frame of the film. In step 355,the reader detects from the scanned image of each frame the opticalsymbols recorded on each frame of the film. In step 360, the readerrecovers the data associated with each of the detected optical symbols.It should be noted that in the context of FIG. 19, step 360 includes thestep of decoding the received data in accordance with an FEC code.

As noted above, a variety of different types of information may bestored on a film. In this regard, attention should now be directed toFIG. 21, which illustrates that a variety of different types ofinformation may be recovered from a film. For example, a film 150 isapplied to reader 500, which provides recovered data via signal 406, asdescribed above. Signal 406 is applied to demultiplexer 595, whichprovides a number of different types of information as represented bysignals 501-1, 501-2 through 501-N. For example, in the context of N=3,signal 501-1 represents the above-noted meta-data, signal 501-2represents video information and signal 501-3 represents audioinformation. It should be noted that demultiplexer 595 merelyillustrates the separation of the recovered data into different types ofinformation. This function may also be performed within a reader and maynot require an actual demultiplexer element.

Reference should now be made to FIG. 22, which illustrates anotherembodiment in accordance with the principles of the invention. Theapparatus shown in FIG. 22 illustrates a recording process that includesdata verification. The apparatus of FIG. 22 includes recorder 600,element 170 and reader 500. A film 150 is applied to recorder 600 forrecording data thereon. For the purposes of this example, recorder 600is similar to recorder 200 of FIG. 12 and stores encoded data on film150. The latter is further processed by element 170, which includeschemical processing and drying as known in the art for making the recordpermanent. The recorded film is then applied to reader 500, whichprovides signal 406 that represents the data recovered from film 150. Asnoted above, the recording process includes data verification. The dataverification is accomplished via the feedback of signal 406 to element140 of recorder 600. FIG. 23 shows an illustrative embodiment of element140, which comprises FEC encoder 605, mapper 115 and buffer & compareelement 610. The input data signal 104 is applied to both FEC encoder605 for encoding and buffer & compare element 610. The lattertemporarily stores a copy of the original data being recorded on film150, e.g., for a particular frame. Mapper 115 performs as describedearlier and selects one of a number of optical symbols, from aconstellation of symbols, as a function of a plurality of data bitsapplied thereto via signal 106. The selected optical symbols areprovided via signal 116. Turning now to the verification process, signal406 represents the recovered data, e.g., for the particular frame, andis also applied to buffer & compare element 610. As such, buffer &compare element 610 includes enough storage capacity to buffer theoriginal data (and original data from following frames) over the timeperiod required for recording a particular frame, processing thatparticular frame (via element 170) and recovering the data from thatparticular frame (via reader 500). Buffer & compare element 610 comparesthe original data for the particular frame to the recovered data forthat particular frame. If an error is detected, i.e., original data hasbeen detected as being “lost”, the lost data is applied to FEC encoder605, via signal 611, for re-recording at a subsequent point on the film.This results in the recorded data becoming fragmented on the film. Toenable a reader to subsequently recover the data from a recorded film inthe correct order, a look-up table (not shown) is written on apredefined portion of the film. This look-up table maps various portionsof the original data to, e.g., frames of film 150, to track anyfragmentation such that a reader can correctly re-assemble the data uponrecovery of the look-up table.

Although the inventive concept was described in the context of amonochrome film, the inventive concept is not so limited. For example,the system described may be extended to record a plurality of records ona multilayer film, such as visible/infrared film, or conventional threelayer color film. The additional data records may be used to support amulti-axis coding scheme with an N-dimensional constellation where “N”is the number of separate records. In this case, N layers, each using2^(M) gray levels would provide (M)(N) bits. It should be noted thatthere may be limitations on reading pixels directly behind a densepixel, but staggering of the records or placement coding rules couldimprove pixel separation on each layer while still providing usefulmultiplication of the overall storage density. Indeed, multiplefrequency ranges or infrared (IR) layers can significantly improveefficiency or packing density.

Thus, various combinations of pixel size and number of density levelsare possible in accordance with the principles of the invention.Different film stocks, processing technique, recording and readingapparatus, may all affect the best choice(s) of pixel size and number ofdensity levels.

As described above, the inventive concept can be applied to any areasuch as, but not limited to, entertainment (media content, e.g., movies,audio, etc.), medical imaging, satellite/geographical imaging; security,historical archives, long-term record keeping, consumer privatearchiving, etc.

Further, the preferred embodiment has been described in terms of 35 mmmovie film, segmented into frames, possibly with intermittent motion andpossibly with shuttering. This is convenient in that it permits the useof the most commonly available film stocks, and a wide range ofequipments designed for use with such film stocks. However, theinventive concept is not so limited and may be applied to other types offilm stocks, including film sheets, to apparatus that does not segmentthe film into frames, but that may use alternative segmentation or nosegmentation, and to apparatus that moves the film in a continuousmanner rather than with intermittent motion. Other examples of film inaccordance with the principles of the invention are a piece of filmsimilar in form to a paper sheet (e.g., a letter-size or 5″×7″ picturesize).

In view of the above, the foregoing merely illustrates the principles ofthe invention and it will thus be appreciated that those skilled in theart will be able to devise numerous alternative arrangements which,although not explicitly described herein, embody the principles of theinvention and are within its spirit and scope. For example, althoughshown as separate elements in FIG. 12, the encoder and mapper of FIG. 12can be a part of the same element. It is therefore to be understood thatnumerous modifications may be made to the illustrative embodiments andthat other arrangements may be devised without departing from the spiritand scope of the present invention as defined by the appended claims.

1. An apparatus comprising: a mapper for selecting one of a number ofoptical density levels as a function of data applied to the mapper,wherein each optical density level represents a symbol from aconstellation of symbols, and wherein each symbol represents a pluralityof bits of data; and a light source for exposing a film such that theselected optical density level is recorded on the film.
 2. The apparatusof claim 1, wherein each optical density level is associated with adifferent level of gray.
 3. The apparatus of claim 1, wherein the lightsource exposes frames of the film such that at least one frame recordsthe selected optical density level.
 4. The apparatus of claim 1, whereinat least some of the data represents at least a portion of a movie.
 5. Amethod for storing data, the method comprising: receiving data; mappingthe data to a symbol selected from a constellation of symbols andwherein each symbol represents a plurality of bits of data, and whereineach symbol is associated with a respective optical density level; andrecording the symbol on film by creating thereon the respective opticaldensity level.
 6. The method of claim 5, wherein the film is monochromefilm.
 7. The method of claim 5, wherein the symbol represents an opticaldensity level.
 8. The method of claim 5, wherein the optical densitylevel represents a level of gray.
 9. The method of claim 5, wherein therecording step includes the step of recording the symbol on at least oneframe of the film.
 10. The method of claim 5, wherein the recording stepincludes the step of exposing a pixel region of the at least one framefor recording of the symbol.
 11. The method of claim 5, wherein at leastsome of the data represents at least a portion of a movie.
 12. Anapparatus comprising: a mapper for selecting one of a number of opticaldensity levels as a function of data applied to the mapper, wherein eachoptical density level represents a symbol from a constellation ofsymbols, and wherein each symbol represents a plurality of bits of data;and a light source for exposing a film such that the selected opticaldensity level is recorded on the film; wherein the light source exposesframes of the film such that selected optical density levels arerecorded in a checker-board like pattern on at least one frame of thefilm.
 13. An apparatus comprising: a mapper for selecting one of anumber of optical density levels as a function of data applied to themapper, wherein each optical density level represents a symbol from aconstellation of symbols, and wherein each symbol represents a pluralityof bits of data; and a light source for exposing a film such that theselected optical density level is recorded on the film; wherein thelight source exposes frames of the film such that selected opticaldensity levels are recorded in a rectangular like pattern on at leastone frame of the film.
 14. An apparatus comprising: a mapper forselecting one of a number of optical density levels as a function ofdata applied to the mapper, wherein each optical density levelrepresents a symbol from a constellation of symbols, and wherein eachsymbol represents a plurality of bits of data; a light source forexposing a film such that the selected optical density level is recordedon the film; and further comprising an encoder for encoding the datawith an error correction code before selection of an optical densitylevel.